Electronics can be divided into a simple hierarchy consisting of devices such as integrated circuit (IC) chips, packages, printed circuit boards (PCB) and a system. The package is the interface between an electronic device such as a computer chip, and a PCB. Devices are made from semiconductor materials such as silicon. Integrated circuits are assembled into a package such as a quad flat pack (QFP), pin grid array (PGA), or ball grid array (BGA), using wire bonding (WB), tape automated bonding (TAB), or flip chip(FC) bumping assembly techniques. The packaged device is then attached either directly to a printed wiring board or to another type of substrate, which is defined as the second level of packaging.
Ball grid array (BGA) packaging technology is an advanced semiconductor packaging technology, which is characterized in that a semiconductor chip is mounted on a front surface of a substrate, and a plurality of conductive elements such as solder balls are arranged in a matrix array, customarily referred to as ball grid array, on a back surface of the substrate. The ball grid array allows the semiconductor package to be bonded and electrically connected to an external PCB or other electronic devices. The BGA package may be employed in a memory such as Dynamic Random Access Memory and others.
A basic flip-chip (FC) packaging technology comprises an IC, an interconnect system, and a substrate. A function chip is connected to the substrate with a plurality of solder bumps, wherein the solder bumps forming a metallurgical interconnection between the chip and the substrate. The function chip, the solder bump, and the substrate form a flip-chip package. Further, a plurality of balls form a ball grid array (BGA).
Wire bonding can be used to make the electrical connections from chip components such as chip resistors or chip capacitors to substrate. Two function chips and are stacked on top of a plurality of substrate layers. The chips are connected to the substrate by a plurality of bonding gold wires. Other form of wires such as aluminum wire can be used too. The function chips, the gold wire, and the substrate form a wire bonding (WB) package.
Package on Package (PoP) is an integrated circuit packaging technique to allow vertically combining discrete logic and memory ball grid array (BGA) packages. Two or more packages are installed on top of one another, i.e. stacked, with a standard interface to route signals between them. This allows higher density, for example in the mobile telephone/PDA market.
Standard POP structures are based on stacked chips connected to substrate by wire bond or flip chip to form a package. Such PoP structures have a large package size due to wire bond connection and solder bump bridges. Also, package mechanical strength is weak due to wire bond connection.
The drawings, schematics and diagrams are illustrative and not intended to be limiting, but are examples of embodiments of the invention, are simplified for explanatory purposes, and are not drawn to scale.